Biology Questions and Answers

Answer: C

The set of cold-blooded organisms is Snake, Frog, Cockroach.

Cold-blooded (poikilothermic) animals cannot keep their body temperature constant; it changes with the surroundings. Reptiles such as snakes, amphibians such as frogs and invertebrates such as cockroaches are all of this kind.

Each other set contains a warm-blooded animal: birds (parrot, pigeon) and mammals (dolphin, humans, whale) maintain a constant body temperature. The lizard and earthworm in those sets are cold-blooded, but one warm-blooded member is enough to rule a set out.

Answer: C

Gills absorb dissolved oxygen from water.

Fish take in water through the mouth and pass it over the gills. The gills have thin filaments richly supplied with blood vessels, through which oxygen dissolved in the water diffuses into the blood and carbon dioxide diffuses out.

Fish do not take in oxygen from air; that is the role of lungs in land animals. Nutrients are absorbed in the intestine, not the gills. Although some wastes such as ammonia do pass out through the gills, their main function is gaseous exchange.

Answer: A

The animal is the snake.

A snake has a long backbone made of many vertebrae, with many muscles attached to it. By contracting these muscles it bends its body into loops, and each loop pushes against the ground, moving the snake forward. This description follows the NCERT chapter on body movements.

The earthworm and hook worm have no backbone at all; the earthworm moves by alternately contracting and extending its body with the help of tiny bristles. The snail moves with a muscular foot and has a shell, not a backbone.

Answer: D

The greenish black patches are bread mould.

Bread mould, such as Rhizopus, is a fungus. Its spores are present in the air and settle on bread; warmth and moisture in a closed container let them germinate and grow into a network of threads, and the dark spore cases give the patches their black or greenish colour.

Bacteria are too small to see as such patches; they form slimy colonies rather than fuzzy growth. Yeast is also a fungus but grows as single cells and does not form these patches on bread. Mushrooms are fungi with large fruiting bodies, not a growth on stale bread.

Answer: A

A and B are true.

An earthworm has no lungs and breathes through its moist skin, so A is true. A tadpole lives in water and breathes through gills; it develops lungs only during metamorphosis into a frog, so B is true.

C is false. A snake is a reptile with lungs, and it breathes air through them, not through its dry, scaly skin. So the options including C, or saying only A is true, are wrong.

Answer: D

The correct matching is (a)-(iii), (b)-(ii), (c)-(i), (d)-(iv).

A housefly pours saliva on its food and mops up the liquid with its sponge-like mouthparts, so it feeds by sponging (a-iii). A humming bird sucks nectar from flowers with its long beak (b-ii). A cockroach has strong mouthparts for biting and chewing (c-i). Infants feed on their mother's milk by suckling (d-iv).

The other options swap these pairs, for instance giving the housefly suckling or the humming bird biting and chewing, which do not fit how these animals feed.

Answer: A

'Y' could be Cuscuta.

Cuscuta (amarbel, dodder) is a parasitic plant with no chlorophyll. It cannot make its own food, so it twines round a host plant and absorbs food from it through special roots called haustoria.

The other options have chlorophyll. Algae are green and photosynthesise. The pitcher plant is green and makes its own food, trapping insects only to obtain nitrogen. A maple tree photosynthesises like any green tree, even if its leaves turn red in autumn.

Answer: A

Algae can make their own food by photosynthesis.

Algae contain chlorophyll, so like green plants they use sunlight, carbon dioxide and water to make food. They are autotrophs and are important producers in water.

Fungi lack chlorophyll and absorb food from dead or living organic matter, so they are saprotrophs or parasites. Rhizobium is a bacterium that lives in the root nodules of legumes and fixes nitrogen, getting food from the plant. Viruses are not even cells and can reproduce only inside a host.